The central objective of this project is to breed rhesus macaques that are specific pathogen free (SPF- as defined by NCRR in RFA RR-G2-005), MHC typed and genetically characterized to provide research subjects to NIH supported investigators for AIDS related research. This objective will be achieved at the YNPRC National Primate Research Center (YNPRC) utilizing an existing colony of 745 SPF macaque monkeys (produced and maintained since 2002 with the support of NCRR Cooperative Agreement U24 RR 018109) and employing skilled and experienced personnel and proven methods and procedures that have been highly successful to date. The existing SPF rhesus macaque colony will be managed to optimize reproduction, both to provide subjects to AIDS investigators, and to increase its total size via breeding. Additionally, during the first two years of this project phase, we will continue recruitment of young animals from YNPRC non-SPF breeding colonies via appropriate testing and separation. The goal is to ensure the availability of SPF subjects to meet the requirements of AIDS investigators, both Emory based and from other institutions regionally and nationally; this is an objective we have achieved very successfully in the past award period (2002 to 2007). The overall YNPRC goal is to transition to an entirely SPF Field Station based rhesus colony by 2013, progressively replacing the non-SPF rhesus macaques in the colony with SPF animals. This goal, although vital to the interests of the Center (and NCRR) in both scientific and safety terms, goes beyond the scope of the present proposal. Thus, we seek here support for a fixed colony of 500 SPF monkeys although we describe a program that includes 745 animals at the outset and that we intend to increase substantially in the proposed award period. The proposed colony of 500 to be supported by this mechanism is level with the effort in the initial award period and, with supplemental animals from our screening program, is sufficient to meet the requirements of our AIDS research portfolio. The SPF animals in excess of the 500 will be supported from program income associated with the base grant (e.g. per diem and use fees) from NCRR to the YNPRC (P51 - RR00165). As the SPF colony grows the conventional colony will be reduced in size, with the goal of achieving a 100% SPF rhesus breeding colony by 2013.